lanthanum

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Symbol:

La

Atomic Number:

57

Relative Atomic Mass:

138.9055 g mol^-1

Natural Abundance in Lithosphere, hydrosphere and atmosphere:

2 x 10^-3% (mass fraction)

Electron Configuration:

[Xe]5d6s²

Oxidation States:

III

Atomic Radius:

187pm

Covalent Radius:

169pm

Ionic Radius:

103pm (for +3 oxidation state, 6 coordinate)

116pm (for +3 oxidation state, 8 coordinate)

Melting Point:

920°C

Density:

6.16 g cm^-3 (at 20°C)

First Ionisation Energy:

5.577 eV

Reduction Potential:

-2.522V

for La³⁺ + 3e^- a La_(s)

Electronegativity (Allred and Rochow):

1.1

Number of Natural Isotopes:

2

Mass Number of the Most Abundant Isotopes:

138 g mol^-1 a 0.1% abundance

139 g mol^-1 a 99.9% abundance